Description

These functions should only take care of the "site-level" part of things, like:

creating/dropping database tables

populating options

setting up initial content

The idea is to only be required to call wp_insert_site() and then wp_install_site() to get a new site set up.

Before we start working on the two functions, we should discuss what exactly it needs to do. This will have to match what currently happens spread out between wpmu_create_blog() and another function it calls, install_blog(). We should aim to make this consistent and also think about ways to enhance these functions and the functions they use, for example by providing filters to adjust some of these defaults.

This will be a rather comprehensive task, so it does not necessarily need to go in at a similar time as the changes from #40364. We should probably even wait to start it until those changes have been completed. This ticket should just be on the horizon for now, I'd say.